Spark plug



' June 24 1924.

S. G. WARNER SPARK 'PLUG Filed Aug. 2.2. 1921 Patented June 24, 1924.

UNITED STATES SELDEN G. WARNER, l' WT ORANGE, NEW JERSEY.. j

SPARK PLUG.

Application led August 22, 1921. Serial No. 494,299.

To all whom. t may concern:

Be it known that I, SELDEN G. WARNER, a citizen of the United States. and a resident of West Orange, Essex County, New Jersey, have invented certain new and useful Improvements in Spark Plugs, of which 4the following isa description.

y invention relates to spark plugs for internal combustion engines and more particularly to an improved mounting for the insulating members of spark plugs, usually formed of porcelain, which carry the central electrodes, and also to the method of producing such mounting. However, While my invention is especially designed for application to the insulating members of spark plugs, it is also applicable to members formed of insulating material and used for other purposes.

There are at present in general use two types of spark plugs, thel principal difference. between them being in the manner of securing the central insulating member or core in the metallic casing or holding member therefor. In one of these types of spark plugs the insulating member or core is permanently cemented into the casing or holding member; while in the other type the insulating member is clamped in the metallic casing or holding member between gaskets which are usually made of copper and asbestes. Each of these types of spark plugs are open to objection for` several reasons. The type in which the insulating member is permanently cemented in the holding Vmember cannot be disassembled, and accordingly when it becomes fouled with carbon deposit or oil it is extremely diiiicult to properlyv clean the same. Moreover, if the insulating member, which is usually ofv porcelain, cracks or fails` the entire spark plug must be replaced. While the type of spark plug in which the insulating member is clamped in the holding member between gaskets may be disassembled for cleaning or replacement of the insulating member, it is lnecessary in order to make a gas-tight joint between the insulating member and the holding member, to subject the gaskets to a very considerable pressure to conform them to all ofthe irregularities of the porcelain insulating member, and also to conform and fit themy to vthe seat for the insulating member provided in the holding member. These gaskets are usually of soft copper and asbest/os, and the pressure which it is necessary to apply to obtain a tight joint between the holding member and the insulating member is often suiicient to break the latter and is all Vthe more likely to do so on account of the uneven application of such pressure to the insulating member which is largely due to the irregularities in the surface of such member. When a spark plug of this type is disassembled the gaskets frequently become deformed and are also found to be compressed and hardened. Accordingly, on reassembling, much eater pressure must be applied to the gas ets to make them conform to the insulating member and to the seat for the latter in the holding member, and the insulating member is therefore subjected to still greater strains tending to break the same. Furthermore, on reassembling a spark plug of this type, there is no assurance that the insulating member will occupy such a position with respect lto the holding member as to bring the sparking points of the plug in exactly the same relative position as before disassembling, and, as a matter of fact, it very seldom does. Therefore, it is usually necessary after reassembling such a spark plug to change the i relative position of the spaced sparking points or electrodes to adjust the length of the spark gap, which adjustment must always be verified. To make and verification it is necessary to remove the entire spark plug from the engine cylinder.

The principal objects of my invention are to provide an improved form of spark plug which is free from the foregoing objections, which is of asimple and superior construction and which comprises fewer parts than the separable spark plugs now on the market.

More specifically described the principal vfeature of my invention consists in applying to the insulating member or core of a spark plug so as to be practically integral therewith, seating and positioning means preferably in the form of a metalcollar or band which after being applied, is accurately machined or worked to truly tit the recess and seat formed in the holding member for the insulating member. This band or collar is preferably applied to the insulating member so as to permanently grip the same under tension and while this may be accomsuch adjustment plished in several ways, I preferably apply such band or collar to the' insulating member by electro-plating. The rod extending through the insulating member and forming one of the spaced electrodes of the spark plug, may also be and preferably is firmly secured in the insulating member by means of a similar band or similar bands a plied to one or both ends of the insulating member and the adjacent portion or portions of such rod.

Other objects and features of my invention will be hereinafter more fully described and claimed. c

In order that my invention may be more clearly understood, attention is directed to the drawing accompanying and forming part of this specification, and in which:

Figure 1 is a longitudinal sectional View, partly in elevation, of an assembled spark plug in accordance with' my invention;

Fig. 2 is a view in elevation of the insulating member of the spark plug illustrated in Fig. 1, showing the bands or collars formed thereon by electro-plating previous to the finishing or machining of these bands; and y Fig. 3 is a view similar to Fig. 2 after the collars or bands applied to the insulatl tion of said holding member.

ing member have been finished or machined.

Referring to the drawing, and especially to Fig. 1, the spark plug shown comprises the usual hollow cylindrical metal casing or holding member 1 provided at its lower end with the inwardly directed sparking point or electrode 2, and an insulating member or core 3, formed of suitable insulating material but preferably of porcelain, carrying the central electrode rod 4 and rigidly secured in the holding member 1 by any suitable clamping means suchl as a collar or gland v5 threaded into the upper end por- 'Ihe lower end portion of the holding member 1, as is customary, is externally threaded as .indi-- cated at 6, to enable the spark plug to be readily applied to the engine.

'Ihe holding member 1 is provided with y a cylindrical recess and a conical seat 7 at the lower end of such recess, which recess and seat are engaged by a seating and positioning member inthe form of a metal band or collar 8 embracing the insulating member 3 intermediate its ends, and applied thereto so as to be substantially integral therewith, in a manner which will presently be described. The collar or band 8 is accurately finished or machined so that the cylindrical intermediate portion thereof ts,

with `a slight clearance, the cylindrical recess provided therefor in the holding member 1, and so that the conical surface provided at the lower end therof fitsthe conical seat 7 in the holding member with great exactness. The upper end of the collar 7 is also provided with a conical surface opposed to and spaced from the inner end of the electrode 2,y which constitutes the other sparking point of the plug, to form a spark gap of exactly the proper length. The conducting rod or electrode 4 is preferably rigidly secured in the insulating member 3, by means of metal bands or collars 9 and ,10 respectively applied to the upper and lower ends of the member V3 and to the respective adjacent portions of the rod 4 so as to be substantially integral with both the rod and the insulating member. These bands 9 and 10 are preferably applied to the insulating member 1 and electrode rod 4 in the same manner as the seating collar 8 is applied to the insulating member. The upper end portion 11 of the rod 4 hasV a nut 12 threaded thereon between which and the upper end of the insulating member 1 the usual conductor or lead is adapted to be secured.

The band or collar 8 on the insulating member 3 and the recess and seat in the holding member 1 may, of course, be iinished or machined to any desired form or shape to meet varying conditions. The form illustrated has proven very satisfactory in use. The outer surfaces of the collar or band 8 are, however, preferably finished or machined so as to be concentric with the lower end of the electrode rod 4, and asvthis collar is accurately fitted to the recess and seat in the holding member 1, 1t

band or will be apparent that the insulating member grip the same under tension, and preferably s0 that the entire contiguous surface portions of the bands and the member or members to which the are applied will be permanently secure Preferably I accomplish this by shrinking 'on the collars; and while this may be done more or less satisfactorily by first forming collars of the proper size and shape, heating together under tension.V

these collars and properly positioning them over the insulating member, and then cooling the same, I find that it is far preferable to form and apply the collars by electroplating. In this connection it is to be noted that the electro-plating of metal is a shrinking process. In forming the collars or bands 8, 9 and l0 by electro-plating, I preferably procesd as follows with especial reference to very thin film` or blush of conducting material is applied in a suitable manner to each portion of the insulating member on which it is desired to electro-plate a metal band or collar, these films being represented b reference characters 8", 9" and 10". Vlhile such a film may be of various Amaterials, I employ a metal such as silver, and preferably deposit the metal in the form of a mirror by any of the well known methods of forming metallic mirrors. If desired, the entire insulating member may be coated with such a film or mirror, and the portions which are not to receive the collars or bands 8, 9

and 10 may then be coated with varnish,-

wax or other insulating material, or the conducting film or mirror may then be removed from such portions. The insulating member is now immersed in the electrolyte of a suitable electro-plating cell capable, upon the passage of electric current therethrough', of depositing the metal, for example, copper, of which it is desired to form the bands 8, 9v and 10. The insulating member is left in the electrolyte or plating bath until rings or bands 8', 9 and 10 are electrolytically dei posited thereon of a suitable thickness from which to finish or machine the same to the desired forms, which are indicated in dotted lines in Fig. 2. The insulating member is then removed from the plating bath and the bands 8, 9 and 10 are finishedor machined o produce the finished article shown in The process described above insures substantially perfect and rigid union of the bands or collars with those portions of the insulating member' and electrode rod which they cover, for, as a matter of fact, they are shrunk thereon because of the property which metal has upon electro-deposit" thereof, of contracting or being place state of tension.

It is to be noted that the metal seating and positioning collar or band v8 is in perfect union with the porcelain insulating member 3, and absolutely conforms to all its surface irregularities, however minute. This insures that strains which may-'abe transmitted through this seating band, such as those caused by tightening the clamping collar 5 of the spark plug, will be uniformly distributed over the surface of the insulating member and throughout its interior. Breakage off-the porcelain insulating members of spark plugs is frequently caused by high and low s ots on their surface receivlng unequal strams and thus forming unbalanced mechanical couples. My improved construction eliminates these couples, distributes the strains and balances them. However, it is to be borne in mind that in my construction, practically all strains due to clamping the insulating mem in position in the holding member, are tak n by the metal collar or band 8, and the insulating member is thusy `relieved of undue pressure which might replu Vlxile I have specifically shown and described my invention as appliedl to s ark t plugs,- it is to be understood that some o the features thereof are capable of other applications. It is also to be understood lthat the embodiment of the invention shown and described herein and also the method described above, are subject to various changes and modifications' without departure from the spirit ofthe invention or the scope of the appended claims.

Having now described my invention, what I claim as new and desire to protect by Letters'Patent is as follows:

1. A spark plug insulating member having a seating member embracing the same and electrolated thereon.

2. A spar plug insulating member having an electrode rod extending therethrough and a metallic band electro-plated-on one on, and a band or collar electro-plated on said lm.

A spark plug insulating member havl ing a metallic mirror" formed thereon and embracing the same,.and aband or collar electro-plated on said mirror.

6. VA spark plug insulating member having a silver mirror formed thereon and embracing the same, anda metallic collar elecyadjacent portion of g tro-plated on said mirror,vsaid collar being finished to accurately t a seat therefor in the holding member of the spark plug.

7. The method of providing a spark plug -5 insulating member with a collar gripped thereon under tension which consists in depositing on such insulating member a thin ilm or blush of conducting .material embracing such member, and electro-platlng a band or collar on'said conducting film.

8. The method of providing a spark' plug insulating member with a collar grippedv thereon under tension, which consists in chemically depositing thereon a thin lilm or blush of conductingmaterial embracing ,the same, and electro-plating'a band or collar on said conducting film.

9. The method of providing a spark plug insulating Amember Witha collar gripped thereon under tension, which consists in formin on such member a metallic mirror embraclng the same, and velectro-plating a band or collar on lsaid mirror.

10. A spark plug comprising a tubularv holding member provided with aseat, and an insulatin member carrying one of the spark plug e ectrodes, said insulating member bein provided with a metallic collar electro-A ated thereon, said collar being inished to accurately iit said seat, and said insulating member being secured within said holding member with said .collar in engagement with said seat.

This specificationsigned this th' day o August, 1921.

SELDEN G. WARNER. 

